How do I remove IE 11 & install IE 10?

I am helping a friend setup a newly purchased PC which upgraded to Windows 8.1 during setup. This installed IE 11. The website on which his wife reports hours worked is not compatible with IE 11 (only through IE 10). I tried compatibility view but no joy. IE 11 is not uninstallable but can be disabled via the "Turn Windows features on or off" function in "Programs and Features". If I disable it can I then install IE 10 or does something more need to be done? Different browser is not an option.

Has she tried an alternative browser for now until the site is update for the latest browser? Sorry, I did not see you statement about a different browser.

If you have a valid unused Win 7 or Win 8 license, you could set up a dual boot scenario so she could sign on to the other browser for this site. Perhaps this work around will help until the site is updated to use this new browser.

Note that a significant change was made in the user agent string 'browser string' - the browser identity that is sent to the site- between IE10 and IE11. IE11 doesn't now even identify itself as 'MSIE'.

Some sites don't handle this string 'correctly' or are not updated, perhaps as you suggest. It is possible to change the browser string a ruirib suggests. However, you might get other possible issues. It's worth a try to eliminate this as an issue.